dept of labour methyl bromide study

8/6/2019 Dept of Labour Methyl Bromide Study

1/28

Workplace Group, Occupational Safety andHealth Service

Monitoring Report: Use of Methyl Bromide at

the Port of Nelson

May 2005


2/28

This report has been prepared solely for the benefit of Workplace Group, Occupational Safety

and Health Services of the Department of Labour.

The report may be made available to other persons for an application for permission orapproval or to fulfil a legal requirement.

Quality Assurance Statement

Workplace Group, Occupational Safetyand Health Service

Prepared by:Mike Lewis Occupational Hygiene Specialist,Workplace Group

Monitoring Report: Use of MethylBromide at the Port of Nelson

Peer Reviewed By:Derek Stannard, MWH New Zealand Ltd

Project Sponsor:Keith Stewart, Service Manager BSU,Workplace Group

Approved for issue by:Mike Cosman, Manager National Operations,Workplace Group, May 2005

Department of Labour, Workplace GroupOccupational Safety and Health Service3rdFloor, 203-209 Willis StreetPO Box 27-463Wellington, New ZealandPH 04 385 7771FX 04 382 9159


3/28

Status Final May 2005MeBr Report.pdf

Workplace Group, Occupational Safety and Health ServiceMonitoring Report: Use of Methyl Bromide at the Port of Nelson

Contents

1. Background..............................................................................................................................11.1 Introduction...................................................................................................................1

2. Purpose....................................................................................................................................22.1 Port of Nelson Activities................................................................................................2

2.1.1 Sawn Timber Fumigation.................................................................................. 22.1.2 Staggered fumigation. ...................................................................................... 32.1.3 Raw Timber Fumigation...................................................................................32.1.4 Shipping Container Fumigation........................................................................ 32.1.5 Storage.............................................................................................................42.1.6 Timber Export Volumes.................................................................................... 42.1.7 Usage Rates.....................................................................................................4

3. Methodology............................................................................................................................44. Risk Assessment......................................................................................................................5

4.1 Methyl bromide.............................................................................................................54.2 Sources of Production of Methyl Bromide.....................................................................64.3 Toxicology of Methyl Bromide....................................................................................... 64.4 Possible Route of Human Exposure.............................................................................7

5. Monitors...................................................................................................................................75.1 Direct Reading Instruments. .........................................................................................7

5.1.1 Halide Lamps...................................................................................................75.1.2 Photo Ionization Detector (PID)........................................................................ 85.1.3 Colorimetric tubes.............................................................................................8

5.2 Monitor Selection..........................................................................................................95.2.1 PID...................................................................................................................95.2.2 Colorimetric tubes ............................................................................................95.2.3 Halide lamp......................................................................................................95.2.4 Limitations........................................................................................................95.2.5 Instruments.....................................................................................................10

5.3 Atmospheric Testing...................................................................................................105.3.1 Background VOC Measurement.....................................................................105.3.2 Fumigation......................................................................................................115.3.3 Gas Release / Ventilation............................................................................... 115.3.4

Shed Clearance..............................................................................................12

5.3.5 Personal Protective Equipment ...................................................................... 12


4/28

Status Final May 2005MeBr Report.pdf

5.3.6 Results...........................................................................................................135.4 Discussion..................................................................................................................14

5.4.1 Limitations of Method..................................................................................... 156. Conclusions...........................................................................................................................167. Future Work...........................................................................................................................178. Recommendations.................................................................................................................18

8.1.1 Exclusion Zone...............................................................................................188.1.2 Stack Ventilation.............................................................................................188.1.3 Flue Height.....................................................................................................198.1.4 Shed Clearance..............................................................................................198.1.5 Personal Protective Equipment ...................................................................... 19

9.

Appendices............................................................................................................................20

9.1 List of Figures.............................................................................................................20


5/28

Workplace Group, Occupational Safety and Health Service

Monitoring Report: Use of Methyl Bromide at the Port of Nelson

Status Final 1 May 2005MeBrReport.doc

1. Background

1.1 Introduction

Residents and businesses adjacent to the Port of Nelson had raised concerns about the potentialfor exposure to methyl bromide during the fumigation operation undertaken at Shed 2. Somehave attributed health concerns to the practice of releasing the fumigant into the generalenvironment, and have described various odours and health symptoms immediately after thecovers are removed from the fumigated sawn timber stacks.

Recently, the Regional Public Health Unit have been undertaking a cluster study of motor neurondisease (MND) deaths in Nelson. One goal of the study was to determine whether a causal linkcould be established between MND and exposure to methyl bromide, and whether the incidenceof MND in Nelson has increased against the national average.

Bio-security agreements with export countries dictate that raw logs and sawn pinus radiata timberproducts are fumigated during theArhopalus trisis (burnt pine beetle) flying season from Octoberto March each year. The adult beetles shelter in the stacks of timber, and if introduced, couldcause damage to overseas domestic timber production.

Historically, the fumigation operation had been undertaken in two locations at the Port of Nelson;Shed 2 and the ANZTA shipping store, both positioned at the western and eastern borders of the

port respectively.

Occupational Safety and Health were to undertake an assessment of the Shed 2 fumigationoperations, however the planned survey was postponed as the operation was moved to Shed 3after a meeting held at the Port on the 4th of March. (See Figure 3, appendices, page 26)

The move was planned to occur in November 2005, however the timeline was brought forwarddue to

a) The withdrawal of the ANZTA Shipping Company from the Port of Nelson; ANZTAundertook parallel fumigation operations at the port. Their withdrawal meant that the twofumigation operations were combined into one location and Shed 2 was identified as no

longer suitable for the task due to the increased quantity of timber.

b) The identified need for more efficient extraction ventilation system to meet the projectedincreased quantities of methyl bromide now to be used for the fumigation of thecombined timber stacks.

As a result, the survey undertaken between the 14th and the 18th of March 2005 was performedon the new Shed 3 location.

It should be noted that due to the changes in the operation, it would be difficult to draw aconclusion from historical factual or anecdotal evidence regarding the possible exposure of

workers or others to methyl bromide as a result of the Shed 2 operation.


6/28




2. Purpose

To evaluate methyl bromide exposure to workers at the Port of Nelson, from the fumigationoperation undertaken at Shed 3.

2.1 Port of Nelson Activit ies

2.1.1 Sawn Timber Fumigation

The timber is delivered to Shed 3 some 12 to 24 hours prior to shipping. This allows for thefumigation, off-gassing, and uncovering of the timber in time for load-out which must be

performed during daylight hours when the beetle is less active and is not attracted to the portlights.

Prior to work, signs are erected to alert port staff and visitors about the fumigation, and expectedventilation date and time.

Polyethylene tubing is placed in the stacks before the timber is covered with a non-permeableplastic sheeting or tarpaulin. Multiple sheets are battened and clipped together to provide a gastight seal. The edge of the sheeting is weighed down with a water-filled tubing to prevent leakageof methyl bromide. This acts as a physical barrier to the insects in addition to the chemical barrierafforded by an insecticide surface-spray applied at the edges of the sheeting.

Methyl bromide, when compressed, becomes a liquid state and remains so when released fromthe storage cylinder. To ensure a full conversion from the liquid to the gas phase, the material isheated via a hot water immersed coil. The resulting gas is delivered to the stack via a manifoldand polyethylene tubing. The methyl bromide cylinder is weighed pre and post delivery to ensurethe correct amount of gas is introduced to the stack. Quantities of 170-280 kg of gas are oftenrequired to achieve the under cover concentration of 48gm/m3(approximately 1000ppm).

The operators detect for leaks or tears in the cover using a halide meter or photo-ionisingdetector (PID). Holes in the fabric are repaired, and post detection is performed to confirm thepresence of a gas tight seal.

The shed is then closed and locked, with signs at the entrances to the building warning offumigation is in progress. A holding period of 12 24 hours is placed on the shed to ensureeffective fumigation of the timber.

Once the holding period has passed, and prior to ventilation of the stacks, an exclusion zone of50 meters is set around Shed 3; the 50-meter exclusion zone is an arbitrary distance that wasagreed to in the Port of Nelson users forum, and the Port Code of Practice.

When the immediate area has been cleared of port staff and visitors, fumigation staff enter theshed wearing Self Contained Breathing Apparatus (SCBA).


7/28




The water tubing is drained, and the timber is ventilated with the assistance of an extraction fanlocated at one end of the stack. The fan draws fresh air the full length of the stack, and isexhausted via an 11m high flue into the atmosphere.

When ventilation is completed, the remaining doors of the shed are opened, and the covers arewithdrawn from the stack either by hand, or via a forklift.

Gas testing is undertaken using either a Photo Ionization Detector (PID) or colorimetric tubes todetermine the residual levels of methyl bromide in the atmosphere inside and immediatelyadjacent to the shed. The fumigation staff gives clearance for entry by port staff and stevedoresonly when atmospheric levels are below the agreed standard (currently 5ppm methyl bromide).

The operators wear Full Face Masks with AX methyl bromide canisters or Self ContainedBreathing Apparatus during operations where there is a risk of exposure to methyl bromide; i.e.during the gas introduction, leak detection, gas release and post fumigation clearance phases of

the operation.

2.1.2 Staggered fumigation.

The common fumigation withholding period and concentration is 12 hours at 48gm/m3 for generalexport commodities. However, sterilisation fumigation is required for stacks of timber that havebeen held at the sawmill for an extended period of time. In this case, the stacks are fumigated at80gm/m3 and withheld for a minimum of 24 hours.

So that both lots of timber are available for a scheduled shipping date, the sterilisation and normal

fumigations are staggered. This requires the operator to introduce methyl bromide into thesterilisation stack, then return 12 hours later to conduct the fumigation of the normal export timberstack.

As there is a potential risk of exposure to errant concentrations of methyl bromide in the generalshed environment, the operators wear SCBA during the preparation and fumigation of the 12 hourstack; i.e. the process of cover placement, clipping, seal placement, and during the gasintroduction phase as mentioned previously.

2.1.3 Raw Timber Fumigation

A similar operation is undertaken at the port for raw logs. The logs that are to be loaded on theships deck are fumigated under covers whilst those logs to be loaded below deck are typicallytreated at sea with aluminium phosphide.

This operation falls outside of the scope of the report, and will require a separate assessment at alater date.

2.1.4 Shipping Container Fumigation

Containers are fumigated in-situ. The gas is introduced in a similar manner as the timber stacks,with the containers being sealed for a period of 12 hours prior to the doors being opened and thegas released.


8/28




Exclusion zones and warning signs are posted near the containers during the operation.

This operation falls outside of the scope of the report, and will require a separate assessment at alater date.

2.1.5 Storage

When not in use, the methyl bromide cylinders are secured in a container adjacent to thefumigation shed, or on an enclosed and locked trailer. Both the container and trailer havesignage alerting to the presence of methyl bromide. Only fumigation staff has access to thecontainer and trailer.

Full cylinders are collected from the Mainfrieght depot, and empties returned for shipping andrefilling overseas.

The cylinders are under constant supervision during the fumigation process.

2.1.6 Timber Export Volumes

In 2003, the Port of Nelson exported a total of 184,429 m3 of sawn and raw timber to China(111,760) and Australia (72,669)1.

2.1.7 Usage Rates

Sawn timber is treated at a concentration of 48 gm/m3 for export to Australia; raw logs are treatedat a higher rate of 120gm/m3 for the Chinese market.

This equates to approximately 196.41 tonnes of methyl bromide used at the port for the year2003.

By comparison, the New Zealands usage rate is 0.3% of the estimated worldwide tonnageof methyl bromide used (65,304 tones); United States is the majori ty user at 22,700 tonnes.

3. Methodology

Literature searches where undertaken to determine the toxicity and human health effects ofmethyl bromide, its worldwide application, production and use, concentrations applied to variouscommodities prior to export, the method of delivery, and physical characteristics of methylbromide.

Information was sought from the fumigator (Genera / Nelson Pest Control) regarding theirprocedures and work practices, withholding and clearance times, and the application of the Portof Nelson Code of Practice.

1 Glassey, K; Issues Paper for Methyl Bromide, 11 January 2005, Ministry of Agriculture and Fisheries, New ZealandGovernment.


9/28




A site meeting was held between the fumigator, Port of Nelson, the stevedoring services, PortSafety Officer, and Applied Research Services Limited. The meeting outlined the samplingmethodology, the location of the ships and port operations relative to Shed 3, and to determinethe ventilation start time in order to accommodate the arrival of the car carry ship and the postfumigation load out of timber from Shed 2 and Shed 3 (See Figure 3, appendices, page 26).

A preliminary site visit was conducted to mark the internal and external data set locations, and tomap the area (See figure 6, appendices, page 29).

Information was sought from Applied Research Services Limited regarding past sampling andanalysis surveys conducted at the Port.

Selected gas detection technologies were assessed for their performance in the field. Theirlimitations of detection and error ranges were taken into account during the measurement of themethyl bromide, and are discussed further in this report.

The calibration certificates and serial numbers for photo ionization detectors (i.e. ToxiRAE andMultiRAE plus) were inspected and recorded.

4. Risk Assessment

4.1 Methyl bromide

Synonym: BromomethaneCAS RN No: 74-83-9UN: 1062Chemical formula: CH3BrMolecular Weight: 94.95State: liquefied gas, in pressure cylindersRelative density (air=1): 3.27 (heavier than air)Calculated relative density during fumigation (air =1): 1.028 (slightly heavier than air)Evaporation rate: very fast

Figure 1. Chemical structure of methyl bromide

A highly toxic fumigant used for soils, grains, silos, mills, warehouses, vaults, ships, buildings,and rail cars, shipping containers, motor vehicles and general commodities2. Most commonlyused to fumigate against insect pests and rodents under import and export bio securityagreements.

2 Extoxnet, Extension Toxicology Network, Pesticide Information Profiles, Methyl Bromide; Bromomethane, June1996


10/28




Methyl bromide has 99.5% purity, with hydrogen bromide and water vapour making up the other0.5%. It is a colourless and odourless liquefied gas, with a chloroform-like odour in highconcentrations.

Typically the fumigation rates for export to Australia and Europe range from 48gm/m3 (for 12hours holding time) for general fumigation to 80gm/m3 (held for 24 hours) for sterilisation. Onoccasion, a rate of up to 120gm/m3 has been used for markets in China and in America, thoughthese levels are likely to drop after consultation with the source countries has been completed3.

4.2 Sources of Product ion of Methyl Bromide

Currently three producers account for 71% of the world supply of methyl bromide; these are theAlbemarle Group and Great Lakes Chemical Corporation (USA) and the Dead Sea BromineCompany (Israel). Autofina S.A. (France) is currently the only producer of methyl bromide forWestern Europe4.

World production of methyl bromide has steadily decreased over the years. Bromine (from whichmethyl bromide is derived) is produced in the following countries (in descending order); UnitedStates of America 39%, Israel 38%, China 8%, the United Kingdom 6%, and other countries 9%.

The USA was the leader in the bromine production, accounting for approximately 71% of theworlds total supply in 1973; that figure has steadily dropped over the last few years in attempt tomeet the Montreal Protocol for the reduction in ozone depleting halides by 2005.

However extensions for certain agricultural uses of methyl bromide have been granted for somecountries until 2015, where there is no technically or economically feasible alternative availablefor fumigation of commodities.

4.3 Toxicology of Methyl Bromide

Methyl bromide gas is rapidly absorbed by inhalation, and distributed to a number of organsystems, which include the lungs, adrenal glands, kidneys, nasal turbinate, brain, testes andlipoid tissue5

The central nervous system is a principle target of methyl bromide, with symptoms of nausea,headache, dizziness, lassitude, numbness of the extremities, confusion and feelings of weaknessbeing displayed some 2-12 hours after inhalation. Changes in electroencephalograms (EEG)may be displayed on testing6.

3(http://www.biosecurity.govt.nz/exports/forests/index.htm)4 Phyllis A. Lyday; Bromine; U.S. Department of the Interior, U.S. Geological Survey Minerals Information, 14.1 14.7. (http://minerals.usgs.gov/minerals/pubs/commodity/bromine/130498.pdf) 5 International Program on Chemical Safety (IPCS) Health and Safety Guide No. 86, methyl bromide, World HealthOrganisation, Geneva 1994

6 Methyl Bromide Risk Characterization Document, Volume 1 Inhalation Exposure. Medical Toxicology, WorkerHealth and Safety, and Environmental Monitoring and Pest Management Branches, Department of PesticideRegulation, California Environmental Protection Agency, February 14, 2002.
http://www.biosecurity.govt.nz/exports/forests/index.htmhttp://minerals.usgs.gov/minerals/pubs/commodity/bromine/130498.pdfhttp://minerals.usgs.gov/minerals/pubs/commodity/bromine/130498.pdfhttp://www.biosecurity.govt.nz/exports/forests/index.htm


11/28




No severe effects on the nervous system for those exposed to low-level concentrations of methylbromide over a long period of time have been noted in humans, however animal studies haveshown injury can occur7.

The half-life of methyl bromide in blood (as the bromine ion) is 2-15 days (average of 12 days)with normal levels in serum or plasma given at


12/28




Although an industry standard, the use of the halide lamp for monitoring should be discouraged infavour of more accurate direct reading electronic halide meters.

5.1.2 Photo Ionization Detector (PID)

The PID measures volatile organic compounds (VOC) and other toxic gases in concentrationsfrom as low as parts per billion (ppb). The detector is sensitive to a range of chemicals, and doesnot typically distinguish one chemical from another.

The PID uses ultraviolet light to ionize the sample gas in positive and negative ions, which arethen counted by the detector. The charged particles produce a current that is amplified anddisplayed on the meter in parts per billion (ppb) or parts per million (ppm)10.

The particles recombine, and the gas sample exits the meter unchanged, which allows the meterto be used to sample gathering in addition to direct reading measurement.

The meters are fitted with lamps of differing ionization potential (electron volts or eV). The mostcommon lamp used is rated at 10eV and is capable of detecting approximately 230 differentcompounds, including methyl bromide.

The meter is calibrated against a known concentration of isobutylene, which has a base-linecorrection factor of 1.00. When measuring a single gas, a specific correction factor is applied tothe reading to give an accurate record of the atmospheric concentration. For example, methylbromide requires a correction factor of 1.70 to be applied to the displayed isobutylene equivalentreading to give the actual concentration in air11.

The difficulty arises when multiple or unknown gases are being measured. No single correctionfactor can be applied to the mixture, and the reading can only be expressed as a total VOCconcentration12.

The error range of the RAE systems PID against the calibration gas isobutylene is quoted as +2ppm.

5.1.3 Colorimetric tubes.

There is currently no known direct reading meter sensitive to methyl bromide alone. However,direct reading colorimetric tubes (for example Gastec, Kitigawa and Drager) that are specificallysensitive to methyl bromide are available.

The methyl bromide tube is in fact two tubes; a presample filter (for humidity) and the analytesection that gives a stain or colour change in the presence of the desired gas. The methyl

10 Application Note; RAE systems PID Training Outline.(http://www.raesystems.com/~raedocs/App_Tech_Notes/App_Notes/AP-000_PID_Training_Outline.pdf).11Technical Note (TN-106); Correction factors, Ionization Energies, and Calibration Characteristics.

(http://www.raesystems.com/~raedocs/App_Tech_Notes/Tech_Notes/TN-106_Correction_Factors.pdf).12 Technical Note (TN-102); Facts about PID Measurements.(http://www.raesystems.com/~raedocs/App_Tech_Notes/Tech_Notes/TN-102_PID_Facts.pdf).
http://www.raesystems.com/~raedocs/App_Tech_Notes/App_Notes/AP-000_PID_Training_Outline.pdfhttp://www.raesystems.com/~raedocs/App_Tech_Notes/App_Notes/AP-000_PID_Training_Outline.pdfhttp://www.raesystems.com/~raedocs/App_Tech_Notes/App_Notes/AP-000_PID_Training_Outline.pdfhttp://www.raesystems.com/~raedocs/App_Tech_Notes/Tech_Notes/TN-106_Correction_Factors.pdfhttp://www.raesystems.com/~raedocs/App_Tech_Notes/Tech_Notes/TN-102_PID_Facts.pdfhttp://www.raesystems.com/~raedocs/App_Tech_Notes/Tech_Notes/TN-102_PID_Facts.pdfhttp://www.raesystems.com/~raedocs/App_Tech_Notes/Tech_Notes/TN-106_Correction_Factors.pdfhttp://www.raesystems.com/~raedocs/App_Tech_Notes/App_Notes/AP-000_PID_Training_Outline.pdf


13/28




bromide tube is however cross sensitive to other halides, and may give false positives ifrefrigerant gases etc are present in the area where sampling is being undertaken.

In addition, most colorimetric tubes have a manufacturers stated error range of between 10-25%.As such, the tubes should essentially be used to determine approximate concentrations of aknown atmospheric contaminant, with the results acting as a guide to further investigation ratherthan a definitive measure13.

5.2 Monitor Selection

5.2.1 PID

The instruments of choice were the MultiRae plus (four-gas detector and PID), and the ToxiRaePID. The PID meters gave instantaneous readings, responded to rapid changes in concentration

of contaminants, was applicable to a range of VOC present at the workplace, would alarm ifconcentrations exceeded preset limits, and could datalog the results for later analysis.

All instruments were calibrated against isobutylene, with the ToxiRae having an internalcorrection factor of 1.70 loaded into the meter for methyl bromide. The MultiRae plus had nocorrection factor applied, and remained at the isobutylene equivalent of 1.00.

5.2.2 Colorimetric tubes

Colorimetric tubes were used to confirm the presence or absence of methyl bromide in instances

where the principle source of contamination could not be readily identified. For example, to givea) an estimation of the residual concentration of fumigant at floor level inside Shed 3 and to b)demonstrate the absence of methyl bromide against the detection of VOC inside a forklift cabin,during the post fumigation timber loadout.

5.2.3 Halide lamp

The halide lamp was not used during the survey due to its lack of sensitivity to low levels ofmethyl bromide. The fumigation staff used the halide lamp at the initial stages of gas delivery fordemonstration purposes only.

5.2.4 Limitations

The limitations of the PID and colorimetric tubes are discussed later in this document.

13 California-Arizona Consortium, Labor Occupational Health Program Hazardous Waste Project, Chapter 3 AirMonitoring. University of California, Berkley.


14/28




5.2.5 Instruments

Rae Systems ToxiRae model PGM-30, Serial Number 002546.Calibrated 22/2/2005Due 22/5/2005Correction Factor 1.70 (Methyl bromide CH3Br)Sensor; Photo Ionisation Detector (PID) for Volatile Organic Compounds (VOC)

Rae Systems ToxiRae model PGM-30, Serial Number 006456Calibrated 22/2/2005Due 22/5/2005Correction Factor 1.70 (CH3Br)Sensor: PID / VOC

Rae Systems ToxiRae model PGM-30, Serial Number 006094

Calibrated 15/3/2005Due 15/3/2005Correction Factor 1.70 (CH3Br)Sensor: PID / VOC

Rae Systems ToxiRae model PGM-30, Serial Number 006086Calibrated 15/3/2005Due 15/4/2005Correction Factor 1.70 (CH3Br)Sensor: PID / VOC

Rae Systems MultiRae Plus model PGM50-5P, Serial Number 095 513040Calibrated 14/3/2005Correction Factor 1.70 (CH3Br)Sensors: Carbon monoxide (CO), PID / VOC, oxygen (O2).

Rae Systems MultiRae Plus Model PGM50-5P, Serial Number 095 504593Calibrated 10/2/2005Due 10/8/2005Correction Factor 1.00 (isobutylene)Sensors: CO, PID / VOC, hydrogen sulphide (H2S), O2, Lower Explosive Limit (LEL).

5.3 Atmospheric Testing

The monitoring program was divided into three distinct areas of operation; Background VOCMeasurement, Fumigation and Gas Release / Ventilation.

5.3.1 Background VOC Measurement.

Background measurements of Volatile Organic Compounds (VOC) were taken in Shed 3 duringthe loading and placement of the stacks of timber for fumigation.


15/28




Of note was the presence of levels of VOCs approaching 70ppm measured near stacks offinished timber products held for storage (See Figure 5, appendices, page 28). It is assumed thatthe most likely compound is white spirits that is found in the Low Organic Solvent Preservative(LOSP) timber treatment used to protect pine against rot and insect damage.

Anecdotally, a strong solvent smell also was detected around this product and staff experiencedslight sensations of light-headedness and stinging eyes.

5.3.2 Fumigation

The shed had three stacks of timber under fumigation. Stacks 1 and 2 were due for a 12 hourfumigation and located to the side, and running the full length, of shed 3. The third smaller stackwas due for a 24-hour sterilisation, and was centrally located against the northern wall of theshed. (See Figure 5, appendices, page 28)

All three stacks were due for load out on Wednesday 16 March 2005.

Levels of 0.9 22.3ppm were detected around the stacks during gas introduction, with a level of246ppm found near a tear in the fabric of Stack 3. Once repaired, levels dropped to abackground of 17.0ppm.

No gas was detected at the manifold during the delivery to Stack 1. The gas delivery for Stack 2was conducted from outside of the shed. The gas delivery of Stack 3 had been performed theprevious afternoon.

5.3.3 Gas Release / Ventilation.

The three stacks were ventilated the morning of the load out.

Stacks 1 and 2 were forced air ventilated through the use of the extraction fans located at thenorthern end of the shed, with the inlet plenums at floor level (Figure 4, page 21). The stackcovers were placed over the plenum, and held in place with sand bags. The covers were lifted tocreate an opening of approximately 2.5 meters wide by 1.5 meters at the southern end of thestack to allow fresh air to be drawn in by the extraction fans

The stacks were ventilated for a minimum of 45 minutes before the covers were removed, andthe doors opened.

Stack 2 was afforded additional ventilation through the use of two large industrial fans placed atthe northern entrances to the shed (See Figure 5, appendices, page 28). The fans blew fresh airinto the shed, and down one side of the stack.

Stack 3 was afforded no fan-assisted ventilation. The stack was subject to the previous practiceof removing the covers and allowing the gas to escape into the general workplace environment.

Of note was the performance of the extraction fans. The covers were drawn close to the stacksby the suction effect afforded by the fans. It was noted that the plastic covers on the individualpackets of timber were also drawn in close to the timber; an effect that the fumigation staff had

not witnessed in the Shed 2 operation.


16/28




5.3.4 Shed Clearance

VOC measurements were taken of the background environment to give clearance for portworkers to the shed as per the agreed code of practice. However, the levels were persistentlyabove the adopted 5ppm standard.

Measurements of VOC were taken inside the cabin of the forklift operating inside Shed 3 after thefumigation. Carbon monoxide, and VOC (principally diesel particulate) were measured at 2.0ppmand 5.1ppm respectively.

Colorimetric tubes were then taken to confirm the presence or absence of methyl bromide inaddition to the VOC readings. Nil methyl bromide was detected over two ranges (2-18ppm and10-100ppm) inside the forklift cabin. The tests were conducted over a 20-minute period with nosignificant variance in the results being observed.

Levels of 30ppm were detected at floor level during the initial post fumigation forklift operation.Subsequently, the forklifts were allowed access to Shed 3, however pedestrian traffic wasprohibited from entry until the background levels of methyl bromide were below 5ppm.

5.3.5 Personal Protective Equipment

Fumigation staff and other personnel afforded access to the Shed 3 used full-face masks withmethyl bromide cartridges for errant vapours (e.g. shed inspection once the covers were inplace), and Self-Contained Breathing Apparatus (SCBA) for all other operations deemed at risk(e.g. gas introduction, release and cover removal).

Methyl bromide is difficult to absorb onto activated carbon, the principle component of mostorganic vapour cartridges. The particle is known to migrate through carbon due to its volatilenature, and can show breakthrough after one shift at levels not significantly higher than the WESof 5ppm.

3M have conducted testing of their 60928 methyl bromide cartridge, and have concluded thateffluent levels of 1.0ppm are detectable after the filter is exposed to 10ppm for approximately 20hours. The manufacturer recommends that the cartridge should not be used for longer than oneshift, and in levels not exceeding 5ppm.

SCBA systems are not subject to the same exposure limitations; i.e. they have often been used inatmospheres of toxic concentration with little of no concern to the worker regarding an inhalationhazard. However, they are limited by the amount of air that can be stored in a bottle, the fitnessof the worker, the respiratory and metabolic rates (exertion) and the potential for leakage of airpast the facial seal.

Typically, a bottle can hold enough air for approximately 30 mins of mildly strenuous work,however the time may increase or decrease according to the individual workers physicalcharacteristics.


17/28




5.3.6 Results

Two data sets were taken during the ventilation process: one from inside the shed, the other fromoutside and at a distance of 6 and 12 meters from the walls. (See figure 6, appendices, page 29).

The arithmetic average PID / VOC results, and ranges of measurement are listed in tables 1 and2. Corrected results (for methyl bromide CF 1.70) are listed in tables 3 and 4.

BackgroundLevels

MethylBromideintroduction

Clips andBattensRemoved

FanAssistedVentilation

CoversRemoved

TimberTransportedfrom Shed

Stack 1 5.5 4.2 1.4 8.4 25.6 0.9Stack 2 4.5 0.5 1.8 11.5 24.2 0.1Stack 3 5.5 2.6 1.3 # 146.8 0.1Outside 0.3 * * 0.4 0.9 ** Measurements not taken# Nil ventilation performed on stack 3

Table 1: Averaged VOC results against Shed 3 Activi ties (ppm).

BackgroundLevels




CoversRemoved


Stack 1 3.0 - 17.5 1.9 - 12.5 0.0 - 2.8 1.4 - 12.5 3.5 - 71.1 0.0 - 5.4

Stack 2 2.1 - 8.1 0.5 - 13.1 0.8 - 5.1 4.5 - 16.110.2 -

40.7 0.0 - 0.7

Stack 3 5.1 - 21.8 1.3 - 10.4 0.0 - 5.3 #68.2 -

587.0 0.0 - 0.3

Outside 0.0 2.0 * * 0.0 4.4 0.0 4.5 ** Measurements not taken# Nil ventilation performed on stack 3

Table 2: Ranges of VOC measurements for Shed 3 Activ ities (ppm).

BackgroundLevels




CoversRemoved


Stack 1 9.4 7.1 2.4 14.3 43.5 1.5Stack 2 7.7 0.9 3.1 19.6 41.1 0.2Stack 3 9.4 4.4 2.2 # 249.5 0.2Outside 0.5 * * 0.6 1.5 ** Measurements not taken# Nil ventilation performed on stack 3

Table 3: Averaged results against Shed 3 Activities corrected for Methyl Bromide (CF 1.70) (ppm).

BackgroundLevels




CoversRemoved


Stack 1 5.1 29.8 3.2 21.3 0.0 4.8 2.4 21.36.0

120.9 0.0 9.2

Stack 2 3.6 13.8 0.9 22.3 1.4 8.7 7.7 27.417.3 -

69.2 0.0 1.2

Stack 3 8.7 37.1 2.2 17.7 0.0 9.0 #115.9

997.9 0.0 0.5

Outside 0.0 3.4 * * 0.0 7.6 0.0 7.7 ** Measurements not taken

# Nil ventilation performed on stack 3Table 4: Ranges of measurements for Shed 3 Activities corrected for Methyl Bromide (CF 1.70) (ppm).


18/28




Stack

1

Stack

1(CF1

.70)

Stack

3

Stack

3(CF

1.70

)

Stack2

Stack

2(CF

1.70

)

Outside

Outsid

e(CF

1.70

) background

gassing

clipsremoved

ventilation

coversoff

timberrem

oval

0

50

100

150

200

250

Figure 2: VOC & corrected levels for Methyl Bromide (ppm) against Shed 3 Activities andSample Locations

5.4 Discussion

Figure 2 displays more than the graphical representation of data; it gives the approximate relativeorientation of the stacks as they were placed in the shed. That is, Stack 3 (the smaller stack) wasplaced between the two larger stacks that were ventilated using extraction fans prior to the coversbeing lifted.

The results show that the risk of exposure to VOCs / methyl bromide is low during the gasintroduction phase, and when the battens and clips are first removed from the covers. The riskrises during the ventilation of the stacks, and significantly so when the covers are removed.

However, the results do indicate that with the assistance of the extraction fans, the levels of

methyl bromide released into the general work environment (i.e. Shed 3) can be reduced up to160 times less than the initial undercover concentration of 1000 ppm.


19/28




Stacks 1 and 2 had been ventilated for a period of 45 mins before the covers were removed; thisclearly is not long enough to reduce the levels of all VOCs to below the exposure standardapplicable to the different solvents present in the timber stacks (including methyl bromide).

However, an increase in the run time of the extraction fans would address this shortfall, and thereis every possibility that the levels of residual methyl bromide (and other volatile organics) underthe covers could be at or lower than the relevant exposure standard.

Of note, was the existence of the high background levels of VOCs in the shed prior to anyfumigation work being undertaken. Levels of between 3.0 21.8ppm (with a peak of 127ppm)indicate that other volatile organic compounds were present. A possible and yet unconfirmedsource of the VOCs is the timber preservatives and antisap stain chemicals used in the finishedpine products, principally the white spirits component of the LOSP treatment.

Port side workers and fumigation staff alike have reported smells akin to that of kerosene orsolvents in and around the stacks of timber handled at the port. They have reported immediatesymptoms and health effects such as stinging eyes, difficulty in breathing, and tingling of the lipswhen near timber treated with Low Organic Solvent Preservative (LOSP), Copper ChromeArsenate (CCA). Similar effects have been reported near glued Laminate Veneer Lumber (LVL)and painted or primed finger jointed facia board.

The existence of the background VOCs, and persistent levels detected post treatment, may gosome way to explaining the smells coming from the timber stacks for a fumigant that otherwisehas no odorant properties.

5.4.1 Limi tations of Method

The principle limitation is the absence of a singular direct reading device that is sensitive tomethyl bromide alone.

Though direct reading colorimetric tubes are available for methyl bromide, they are sensitive toother halides, and often carry an error range in the order of 25-30% resulting in false positives ornegatives.

Colorimetric tubes give a snap shot concentration of the contaminant, and as such are not

sensitive enough to show peak and trough fluctuations.

They are open to interpretation by the user, who has to estimate the borderline of colour changebetween the reacted and unreacted analyte in the tube.

That being said, they have some merit as a confirmatory test for the presence or absence ofmethyl bromide when used in conjunction with a direct reading device sensitive to a range ofcontaminants such as the Photo Ionization Detector (PID).

The Photo Ionization Detector (PID) has one distinct flaw; is cannot distinguish one ionisable gasfrom another. If there are multiple contaminants present then the PID can at best give a total gas

concentration in isobutylene equivalents (the baseline volatile organic compound from whichothers are derived).


20/28




This was certainly the case at Shed 3. At best there was the likely existence of white spirits(LOSP), diesel particulate, methyl bromide, formaldehyde, paint solvents (toluene, xylene,turpentine) and natural pine oils (pinenes) present during the 4 days of measurement.

Some compounds can be excluded from measurement with the use of lamps with differingionisation potentials. For example, all the PIDs used during the sampling were fitted with 10.6eV(electron volt) lamps, which excluded formaldehyde (present in the glue used with LVL timbers).However this lamp includes diesel, most solvents, and some pinenes, making it difficult toassociate the levels of VOCs with methyl bromide alone.

In addition, factors are required to be applied to the readings given by the PID to provide acorrected reading for the chemical being measured. In the instance with the ToxiRAEs, thecorrection factor of 1.7 was applied at calibration, thus making the unit sensitive to methylbromide alone. This does not exclude the other VOCs that the meter will read, but allows the

user to measure for a known compound without having to make a manual correction to the dataas was the case with the MultiRAE plus used inside shed 3.

A point to consider. If the unit is given to an untrained operator, who is told that is calibrated formethyl bromide, and they are not aware that the meter is capable of giving a corrected total gaslevel, they will assume that the unit is reading for methyl bromide alone. The fact of the matter isthat they may very well be reading methyl bromide, but not in isolation, and most certainly not atthe levels indicated by the meter.

That being said, the PID is a useful device for performing a trend analysis in real time, and if theoperator is confident that the high levels are most likely due to the target analyte alone (as was

the case with methyl bromide when the covers where first removed) then the results can be reliedupon as an accurate representation of the actual contaminant of interest.

6. Conclusions

Significant changes have been made to the fumigation of sawn and finished pine products at thePort of Nelson (PoN). The Port had recognised the necessity for assisted ventilation of thefumigation sheds, and had installed the two extraction fans firstly in Shed 2, then most recently inShed 3.

The efficiency of the fans has greatly increased with the endwise orientation of the fans relative tothe stacks of timber. The initial assessment of the extraction systems ability to clear the stacksof methyl bromide and associated VOCs was surpassed by the observed performance during thesurvey.

Even with limited ventilation run time of 45 mins afforded to Stacks 1 and 2, the results clearlyshow a significant reduction in residual contaminants compared with Stack 3 (where noventilation was performed).

The suggestion that high levels of methyl bromide existing some distance away from the shed

during gas release, ventilation and cover removal cannot be supported. Levels of contaminant at


21/28




up to 12 meters from the doors of the shed show averaged VOC levels of 0.9 ppm, with correctedlevels for methyl bromide of between 1 - 5ppm.

Peaks levels of 4.5ppm (VOC) and 7.7 ppm (methyl bromide) were briefly detected at thenortheast side of the shed when the covers were first removed. This is not unexpected, giventhat portable industrial fans located at the northern doors were further ventilating Stack 2.

Caution is needed when interpreting the corrected results for areas not immediately adjacent tothe stacks. A high degree of confidence can be applied to the levels of methyl bromide measuredafter the removal of the covers, and to some large extent, the initial release of the gas when thewater seal is drained. The relative concentration of methyl bromide to other VOCs would be highin these instances, given that the gas is captured under the covers, and has not had the chanceto dilute into the general atmosphere.

The same degree of confidence could not be applied to the period of time after the covers have

been removed, and to the area immediately adjacent to the shed doors. Methyl bromidedissipates quickly into the atmosphere, and as there is a finite concentration of the material, therelative concentration of methyl bromide to VOC would drop significantly. That is, the virtualreservoir of VOCs leaching from the timber exists well after the methyl bromide has dropped tonearly undetectable levels and these could provide a false positive peak above the workplaceexposure standard when using a PID alone.

The difficulty is that the PID instruments cannot differentiate between one form of VOC (whitespirits for example) and the existence of methyl bromide. There is the distinct possibility that thepeak VOC level recorded at the north-eastern door may very well have come from a stack oftimber found to be releasing quantities of LOSP vapour (up to 78 ppm) even before fumigation

operations commenced.

The exposure to methyl bromide during the entire fumigation operation is well documented andcontrolled. The reconfiguration of the extraction fans has significantly increased the efficiency ofthe stack ventilation, which can only improve with some minor engineering improvements.

Finally, an observation on the effectiveness of the 50-meter exclusion zone agreed to in the PortCode of Practice. It is acknowledged that the zone perimeter was set prior to the ventilationprocess, marked with traffic cones and signs.

The difficulty in maintaining the exclusion zone soon became clear, when port container forklifts

required access to refrigerated reefers that were located inside the zone adjacent to the shed.Limiting the traffic during load out of the Maersk Sealand had the potential of attracting significantpenalties to the Port of Nelson, and for no apparent benefit regarding the potential exposure ofworkers to methyl bromide, based on the data to hand.

7. Future Work.

This survey must be placed into context. The data sets were taken during particularmeteorological conditions, fumigation quantities, port operations against a single event for

ventilation (where the extraction time has since been increased), and where the Shed 3operations had been instigated less than a week prior to the survey.


22/28




Further monitoring is required to gain a comprehensive picture of the performance of the Shed 3extraction system, and the reduction of methyl bromide in the immediate work environments.These may include plume studies, and flow rates of air in and around the stacks.

In addition, the survey has raised questions regarding the off gassing of timber preservatives intothe workplace environment, pre, during and post fumigation, with particular regard to the residualwhite spirit content in LOSP treated timbers. The potential health risks to port workers andfumigation staff alike needs to be assessed against a robust occupational hygiene survey,targeting the like of LOSP, formaldehyde etc.

The study may include health questionnaires, personal monitoring of port workers and fumigationstaff for exposure to VOC, and point source grab samples for analysis by gas chromatography ormass spectroscopy. Measurement of the residual preservative chemicals in pre fumigated timberand the atmospheric concentration of volatile chemicals released pre and post fumigation would

be made in addition to the assessment of under cover chemistry during fumigation and thepossible interaction of the methyl bromide with the likes of white spirits found in LOSP treatedtimbers.

Finally, these projects will need to be conducted independent of further surveys into raw log,container, ships hold and commodities fumigation to gain intelligence regarding the fumigationindustry as a whole and the duration of exposure of workers and others to methyl bromide undervarying operational parameters.

8. Recommendations

8.1.1 Exclus ion Zone

In light of the low levels of VOCs measured during the ventilation process, and the difficultiesexperienced by the general port operations in maintaining the exclusion zone during the fumigantrelease and stack ventilation, it is suggested that the current exclusion zone of 50 meters berevised after of further atmospheric testing.

Agreement on the zone location and distance from Shed 3, and times to which the exclusion

zone is applied during ventilation will need to be reached amongst all port side operators andusers, as per the current Port of Nelson Code of Practice.

8.1.2 Stack Ventilation

Fan assisted stack ventilation is to continue in all instances where timber is fumigated in Shed 3.The fumigator has conducted post survey work, and it was found that fan assisted ventilationtimes in excess of 12 hours have dropped the measured levels of VOCs to practicallyundetectable.

In light of this work, the minimum ventilation time for individual stacks of timber should not be lessthan 12 hours, and more, as post ventilation VOC levels dictate.


23/28




8.1.3 Flue Height

Industrial ventilation design dictates that exhaust ports for extraction flues are be at a height of 3

meters or more above the highest point of the adjacent roof. This is to eliminate the potential ofbuilding downwash; i.e. contaminants swirling back down into the work area from whence theycame.

Further more, the exit velocity of the contaminant can be increased through the use of a truncatedcone installed at the top of the flue. This will significantly increase the effective plume ejectionheight to above and away from the immediate port buildings and surrounding areas.

It is recommended that the height of the flue be increased to not less than 3 meters above thehighest point of the Shed 3 roof, that an ejection cone be installed at the top of the flue toincrease the exit velocity, and that a third flue configuration be installed to ventilate stacks oftimber that may be placed on the midline of the shed.

Advice on the specific characteristics of the flue design should be sought from a ventilationengineer.

8.1.4 Shed Clearance

Entry to Shed 3 is prohibited to all personnel (with the exception of the fumigator) whilst thefumigation operation is in progress; this includes the ventilation of the stacks and cover removal.

Only the fumigator or his authorised delegate can issue the shed entry clearance. Preliminarytesting of total VOC using a PID is to be augmented with a confirmatory direct readingcolorimetric tube test. The operator is to be mindful of the error ranges of both instruments duringmeasurement, and is to make adjustments to the entry time erring on the side of caution.

Shed clearance for entry of port staff and others shall not be given until the averaged levels ofVOCs and methyl bromide are at, or below, the relevant Workplace Exposure Standard (WES)for the contaminants.

8.1.5 Personal Protective Equipment

The use of full-face masks and methyl bromide cartridges are to be limited to work where levelsof methyl bromide are not likely to exceed 5ppm. Cartridges are not to be used for more than oneworking shift. Given that methyl bromide will migrate through activated carbon charcoal afterexposure, and that it has no odour or warning properties, cartridges are not to be stored forreuse.

For all other operations, Self-Contained Breathing Apparatus (SCBA) are to be used as theprimary form of respiratory protective equipment. All staff using such equipment are to be givenappropriate training and supervision in the use, care and maintenance of the SCBA and full-face

masks.


24/28




9. Appendices

9.1 List of Figures

Figure 1. Chemical structure of Methyl Bromide (Page 9)

Figure 2: VOC & corrected levels for Methyl Bromide (ppm) against Shed 3 Activities andSample Locations (Page 18)

Figure 3: Port Operations 16th of March 2005. (Page 26)

Figure 4: Relative locations of Shed 3 to container storage and Main Wharf. (Page 27)

Figure 5: Shed 3 Configuration. (Page 28)

Figure 6: Approximate locations of internal and external data sets for Shed 3 (Page 29)


25/28




Figure 3: Port Operations 16th of March 2005.

Koko o Chief

Car carrierMaersk Sealand


26/28




Figure 4: Relative locations of Shed 3 to container storage and Main Wharf.

Holcim Cement


27/28




Figure 5: Shed 3 Configuration.

VentilationFlues / Fans

Industrial Fans

Stack 1

Stack 2

Stack 3

Timber Stora e


28/28



Figure 6: Approximate locations of internal and external data sets for Shed 3

External data sets

Internal data sets

dept of labour methyl bromide study

Documents